I just accidentally re-snapped a shot! Have I overwritten the old one?!

Answer:  No, you can easily recover it.  

While you will only see the newly snapped shot, the old one is still stored, it's just marked as deleted and yes, you can easily restore it!

WHY Is this happening all the time?  I don't understand the workflow...  

Here's the simple explanation.  Whenever you reload a shot, either from the shot manager or the Shot Preview Area the program assumes you are editing a shot and when you snap this shot with modifications, it replaces the old one (though as we mentioned at the top, you can easily recover it) and saves the new one in its place.  

To avoid this, simply change the insertion point in the shot preview area.   Read here for more details.

Okay, how do I go about restoring a shot I accidentally overwrote?

1. Go to the Shot Manager (In Main View go to the Tools Menu, then choose Storyboard Shot Manager) if you are not already there.
2. Click the SHOW DELETED BUTTON (highlighted in yellow in the image below.

3  All Deleted frames will appear with a yellow haze over them to show that they are deleted, and will appear italicized in the Shot Lister to the top left.  See the second frame in the graphic below, which we've additionally added a yellow box around for clarity.

4  Select those deleted frames you want to restore, and the Delete Frame button in the middle of the row of buttons between the shot sequencer and active view will change its text to Restore Frame as shown in the image below:

5  Click that Restore Frame button and it will restore all selected deleted frames.